Studies of copper-modified V?Mo oxide catalyst for acrolein oxidation to acrylic acid

Modification of a V–Mo oxide catalyst by copper improves its catalytic properties due to the formation of a variable composition V–Cu–Mo–O phase with varying the ratio Mo/Me (Me=V+Cu).

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T–Cu–Mo–O, Mo/Me, Me=V+Cu.

     

Influence of the preparation method of precipitated Fe?Mn catalysts on their properties in CO hydrogenation

Studies of the properties of precipitated Fe–Mn catalysts in CO hydrogenation have revealed that samples precipitated from iron and manganese nitrates by sodium carbonate are more selective to olefins than those precipitated by ammonia. Difference in the catalytic properties is due to the different phase compositions of the catalysts.

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CO , . , , , , . .

     

Thermoanalytical investigations of some industrial wastes produced in steel works

The experiments involves three types of industrial wastes produced by iron works, which create serious hazards to the natural environment: (1) paint-shop sludge, (2) oil-polluted diatomite, and (3) oil-polluted scale. The choice of an appropriate and safe storage method should be based on extensive physicochemical examination.DTA, in combination with other data, allows characterization of the combustible properties of wastes. Thermoanalytical measurements were carried out in a dynamic air atmosphere. Enthalpy values were calculated from peak areas of DTA curves. Thermoanalytical data were compared with calorimetric results obtained with an oxygen bomb.

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Zusammenfassung Drei Arten industrieller Abtälle eines Stahlwerks, die schwere Umweltbelastungen darstellen, wurden untersucht: (1) Lackiererei-Schlamm, (2) ölhaltiger Diatomit, (3) ölhaltiger Kesselstein. Geeignete sichere Deponien setzen ausführliche physikalisch-chemische Untersuchungen voraus. DTA in Kombination mit anderen Untersuchungen erlaubt die Charakterisierung der Verbrennungseigenschaften der Abfälle. Die thermoanalytischen Untersuchungen erfolgten im Luftstrom, die Verbrennungswärmen wurden aus den DTA-peak-Flächen berechnet. Die Ergebnisse werden mit denen kalorimetrischer Messungen in einer Sauerstoffbombe verglichen.

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- , . , . , - . . . . , .

     

On the structure of surface active centers on CuO

It has been established that surface active centers on CuO can be associated with its surface defects, i.e. surface exits of twinning and screw dislocations where highly reactive oxygen and CO can be coordinated.

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, , CO.

     

Glass transition and crystallization effects demonstrated by thermal analysis of liquid-quenched ternary glasses Te80Ge20−xA x V (AV=Sb,Bi)

In DSC studies of liquid-quenched ternary chalcogenide glasses Te₈₀Ge_20–xA _x ^V (A^V=Sb, Bi), the characteristic temperatures (glass transition and crystallization temperatures) were determined. Changes in the thermal stabilities of these glasses, depending on the element A (Sb, Bi) from group V of the periodic table and on its content in the alloy were evaluated. Moreover, the effect of changes in the glass composition on the glass formation ability expressed by the parameter K_g1 was determined.

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Zusammenfassung In DSC-Untersuchungen abgeschreckter ternärer Chalkogenidgläser des Typs Te₈₀Ge_20–xA _x ^v (A^x=Sb, Bi) wurden die charakteristischen Temperaturen (die GlasÜbergangs- und Kristallisationstemperaturen) bestimmt. Die Änderungen der Thermostabilität dieser Gläser wurden in Abhängigkeit von dem Element A (=Sb, Bi) aus der V Gruppe der Periodensystems und von seinem Gehalt in der Legierung ausgewertet. Ausserdem wurde der Einfluß der Änderungen in der Glaszusammensetzung auf die Glasbildungsfähigkeit, ausgedrückt durch den Parameter K_g1, bestimmt.

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Résumé On a déterminé par analyse calorimétrique différentielle (DSC) les températures caractéristiques (températures de transition vitreuse et de cristallisation), des verres ternaires à chalcogénures formés par trempe à partir du liquide, du type Te₈₀Ge_20–xA _x ^v (A^v=Sb, Bi). On a évalué la variation de la stabilité thermique de ces verres en fonction de l'élément A (=Sb, Bi) du Vème groupe du tableau périodique et de sa teneur dans l'alliage. De plus, on a déterminé l'effet des variations de la composition du verre sur la capacité de formation du verre qui s'exprime par le paramètreK _g1.

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Te₈₀Ge_20–xA _x ^v (A^v=Sb, Bi), , . A(=Sb,Bi) . , K _gl, .

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Research supported by the U. S. National Science Foundation under Grant No. GF 421 76     

Thermal stabilities of new complexes of magnesium nitrate,acetate and phosphate with amide ligands

The thermal decompositions of complex compounds of magnesium nitrate, acetate and phosphate with urea, acetamide and formamide ligands were investigated by means of simultaneous TG-DTA. The thermal stabilities of the complexes depend on the natures of the anions and the amide ligands.

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Zusammenfassung Die thermische Zersetzung der Komplexverbindungen von Magnesiumnitrat-,acetat und -phosphat mit Harnstoff, Acetamid und Formamid wurden durch simultane TG-DTA untersucht. Die thermische Stabilität der Komplexe hängt von den Anionen des Salzes und den Amidliganden ab.

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-,- , . , .

     

TPD study of catalyst surface acidity

Acidity of catalyst surfaces of different nature such as -Al₂O₃, natural zeolite-clinoptilolite, and synthetic zeolite zeokar by adsorption of ammonia over a wide temperature range has been studied. Ammonia is adsorbed on the catalysts with different strengths, as evidenced by the presence of different types of acid sites.

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(-Al₂O₃, - , () . , , .

     

X-ray study of palladium catalysts. Influence of thermal treatment in hydrogen on the phase composition

The thermal treatment of Pd catalysts in a reducing atmosphere of hydrogen leads to interaction of supported metal and support to form solid solutions.

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, .

     

Potential for coal calorific value corrections,dependent on the carbonate mineral type present

In addition to calcite, other carbonate minerals in coal all undergo endothermic reactions on heating, i.e. dolomite, ankerite, siderite, aragonite, magnesite, rhodochrosite, witherite and strontianite. Of these, when determined in air, siderite and rhodochrosite give small exothermic resultants, while the amount of Fe in ankerites affects the actual endothermic values obtained. The magnitude of these carbonate decomposition reactions can be shown by DTA to be different and will need to be allowed for individually in calorific value corrections of coals containing them.

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Zusammenfassung Nicht nur Kalkspat, sondern auch andere in Kohle vorkommende Karbonatmineralien wie z. B. Dolomit, Ankerit, Spateisenstein, Aragonit, Magnesit, roter Braunstein, Witherit und Strontionit gehen bei Erhitzen endothermische Reaktionen ein. Von diesen zeigen Spateisenstein und roter Braunstein exotherme Ergebnisse kleinen Wertes, während der Betrag an Eisengehalt in Ankeriten den jeweils gemessenen endothermischen Wert beeinflußt. Das Ausmaß dieser Karbonatzersetzungsreaktionen kann durch DTA-Messungen als unterschiedlich nachgewiesen werden und muß bei den Kaloriewertkorrektionen für Kohlen, die diese Mineralien enthalten, berücksichtigt werden.

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, , , , , , , , . , , . , , .

     

Stoichiometry as canonical transformation of chemical kinetics

Applying the apparatus of differential manifolds and that of classical conservative point mechanics, it is shown that stoichiometry plays the role of canonical transformations in chemical reaction kinetics.

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, , .

     

Temperature programmed desorption (TPD) of carbon monoxide from cobalt surfaces

Three different binding states of CO on cobalt surfaces have been identified by TPD studies. The energetics of these adsorption states and their relevance in Fischer-Tropsch synthesis are considered.

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CO - . -.

     

Preparation and properties of supported vanadium-phosphorus catalysts studied by chemical analysis and ESR

The preparation of vanadium-phosphorus catalysts is described, showing the considerable influence of phosphorus on the concentration of V⁴⁺ ions. The oxidation properties were studied by chemical analysis and electron spin resonance. Moreover, ESR spectra show a strong influence of moisture on the structure of the catalysts.

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- , V⁺⁴. , . , , .

     

Der Einfluss der Temperaturführung auf die Kinetische Auswertung Nichtisothermer Reaktionen

Zusammenfassung Das Problem der rationellen Lösung des Zeitintegrals stand bei der kinetischen Auswertung nichtisothermer Prozesse häufig zur Diskussion. Nun werden für lineare und nichtlineare Aufheizung gemäß dT/dt=Q·T_b mitb von 4 bis –2 Auswerteverfahren vorgestellt, die in jedem Fall eine vollständige Korrektur derjenigen kinetischen Parameter gestatteten, die durch linearisierte Auswertung erhalten worden sind. Diese Methode der vollständigen Exponentialintegrale zeigt, daß eine klare Abstufung nach dem Typ der Aufheizung besteht. Die notwendigen Korrekturen fürb=1, 2 und 3 sind kleiner als fürb=0 d.h. für lineare Aufheizung. Die vier Korrekturtabellen sind für Verfahren der kinetischen Analyse anwendbar, denen ein Aktivierungsansatz nach Arrhenius bzw. Eyring zugrunde liegt. Die Realisierung nichtlinearer Aufheizprogramme wird empfohlen.

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The problems of rational solution of the time integral in kinetical evaluation of nonisothermal processes have often been discussed. Evaluation procedures are now presented for linear and nonlinear heating according to dT/dt=Q·T^b, withb between 4, and –2. In every case a complete correction of the kinetical parameters is possible if they are obtained by linearized plotting. This method of complete exponential integrals shows a clear graduation with the type of heating function. The corrections necessary forb=1, 2 and 3 are less than those forb=0, i.e. linear heating. Four tables of correction values are applicable to all procedures of kinetical analysis which are based on activation parameters from the Arrhenius or Eyring equations. Nonlinear heating programmes are recommended.

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Résumé On a souvent discuté les problèmes soulevés par la solution rationnelle de l'intégrale du temps dans l'évaluation cinétique des processus non-isothermes. On présente ici des méthodes d'évaluation dans le cas de chauffages linéaire et non-linéaire, selon dT/dt=Q·T^b avecb entre 4 et –2. Une correction complète des paramètres cinétiques est possible dans tous les cas, si ceux-ci ont été obtenus par des fonctions linéarisées. Cette méthode d'intégration complète des exponentielles montre une graduation nette selon le type de la fonction du chauffage. La correction nécessaire pourb=1, 2 et 3 est inférieure à celle pourb=0, c'est-à-dire pour le chauffage linéaire. Quatre tables de correction basées sur les paramètres d'activation des équations d'Arrhenius et respectivement d'Eyring peuvent être appliquées à tous les procédés de l'analyse cinétique. On recommande de réaliser des programmes de chauffage non-linéaires.

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. , dT/t=Q. ^b 4 -2. , . . , b=1, 2 3, b= . . . , , , . .

     

Kinetic isotope effect in proton exchange processes between methanol and water in inert solvents

The kinetic isotope effect in proton exchange between methanol and water in CCl₄ solution was studied by¹H and²H NMR and kinetic IR spectroscopy. The exchange rate increases in the series CD₃OH+H₂O3OD+H₂O3OD+D₂O. It has been concluded that the limiting step of the reaction involves the formation of an H-bonded cyclic intermediate.

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¹H ²H - CCl₄. , CD₃OH+H₂O3OD+H₂O3OD+D₂O. , - -.

     

Effect of calcination temperature on the surface composition of Mo?Fe catalysts for methanol oxidation

XPS studies have revealed a decrease in the concentration of iron atoms on the surface of Mo–Fe catalysts with increasing calcination temperature. From a comparison of chemical analysis and XPS data the Mo/Fe ratios on the surface of catalyst samples at various calcination temperatures have been determined. Comparing the above data with changes in the catalytic activity of the samples examined in methanol oxidation, the conclusion has been made that the active component of the catalysts is a solid solution of molybdenum oxide in ferric molybdate.

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. Mo/Fe . , .

     

Calculation of the energy spectrum of surface oxygen on CuO by the interacting bonds method

Using the interacting bonds model a calculation has been made for the energy spectrum of oxygen on the CuO surface. Dissociative adsorption of oxygen can be realized in one and two-center forms with 9.2 and 60.4 kcal/mol, respectively. Intermediate values of the adsorption heats are attributed to oxygen adsorption on induced and biographic defects. The theoretically calculated energy spectrum of adsorbed oxygen is in reasonable agreement with that obtained experimentally from the dependence of isosteric heats of oxygen adsorption on the surface coverage.

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CuO. - 9,2 60,4 / . . .

     

Kinetics of propylene oxidation in the region of negative temperature coefficients of the rate

Kinetic regularities in the consumption of initial reactants and the accumulation of propylene oxidation products has been studied in the region of negative temperature coefficients of the maximum reaction rate (T=648–723 K). It has been revealed that for prolynene-enriched mixtures (C₃H₆:O₂=3:1) at P-20.66 kPa, the reaction rate is practically independent of the temperature, whereas for poor mixtures (C₃H₆:O₂=1:5) it decreases with increasing temperature.

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a (T=648–723K). , (C₃H₆:O₂=3:1) P=20,66 , (C₃H₆:O₂=1:5) .

     

Investigation of low-temperature regeneration of activated carbon

Granular activated carbon loaded with aniline,o-nitroaniline oro-nitrophenol, regenerated at relatively low temperature (450° in N₂ atmosphere), shows losses of cyclic adsorption performances (about 5 % per cycle) comparable to those occurring with standard thermal regeneration (950° in controlled atmosphere). Adsorbate build-ups and related surface modifications have been determined.

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Zusammenfassung Mit Anilin,o-Nitroanilin undo-Nitrophenol beladene, bei relativ niedriger Temperatur (450° in N₂-Atmosphäre) regenerierte granulierte Aktivkohle, zeigt zyklische Verluste der Adsorptionsleistung (etwa 5 % je Zyklus), welche mit den bei thermischer Standard-Regenerierung (950° in gesteuerter Atmosphäre) vorkommenden vergleichbar sind. Der Aufbau der Adsorbate und die damit verbundenen Oberflächenänderungen wurden bestimmt.

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Résumé Le charbon actif en granulés, chargé d'aniline, d'o-nitroaniline et d'o-nitrophénol, régénéré à une température relativement faible (450° dans une atmosphère d'azote) montre des pertes de rendement d'adsorption cyclique (environ 5 p.c. par cycle) comparables à celles qui ont lieu lors de la régénération thermique standard (950° en atmosphère contrôlée). On a déterminé la constitution des adsorbats et les modifications relatives de surface.

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, , -, - – 450° . , ( 5% ) – 950° . .

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Work supported by IRSA-CNR, contract no. 77.01823.11.

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Thanks are due to Mr. L. Pace for skilful contribution to the experimental work.     

Thermal decomposition kinetics of sodium metaperiodate

Aged and fresh samples of sodium metaperiodate are subjected to thermal decomposition studies in air by TG, DTG and DTA techniques. The kinetic parameters for their decomposition have been evaluated by weighted least squares method using equations of Coats-Redfern, Horowitz-Metzger and Freeman-Carroll. The results indicate that, within the limits of experimental error, ageing did not change the E^* values considerably.

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, . , -, - -. , , , E^*.

     

Study of distribution of elements in the depth of V?P?Co catalyst grain

It has been shown that addition of cobalt to a vanadium-phosphorus oxide catalyst increases the P/V molar ratio on the surface, the surface acidity and the selectivity of butane oxidation. It has been established that in the V–P–Co–O catalyst the probability of the removal of phosphorus from the surface is markedly reduced.

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, , . , V–P–Co–O .